Meter proving system

ABSTRACT

A system and method associated therewith are disclosed for proving and/or monitoring the accuracy of a flow measuring device situated in an active flow path and capable of providing an indication of the rate of flow of fluid therethrough. The system includes storage means for accumulating a predetermined volume of fluid therein and injection means cooperating with the storage means for introducing said predetermined volume of fluid into the active flow path on the upstream side of the flow measuring device within a measured period of time. In a preferred embodiment, the storage means is continually flushed with the product flowing in the active flow path thereby maintaining the temperature and product in the storage means conincident with the temperature and product flowing in the active flow path. Additionally, fluid derived from the active flow path may be utilized for driving the injection means.

[451 July 4,1972

[54] METER PROVING SYSTEM [72] lnventors: Edward L. Wright, Plainfield;Eugene Meseck, Lincoln Park, both of NJ.

Customline Control Products, Inc., Linden, NJ.

[22] Filed: Aug. 18, 1970 [21] Appl.No.: 64,741

[73] Assignee:

[57] ABSTRACT A system and method associated therewith are disclosed forproving and/or monitoring the accuracy of a flow measuring devicesituated in an active flow path and capable of providing an indicationof the rate of flow of fluid therethrough. The system includes storagemeans for accumulating a predetermined volume of fluid therein andinjection means cooperating with the storage means for introducing saidpredetermined volume of fluid into the active flow path on the upstreamside [52] U.S.C|. ..73/3, 73/194R of the flow measuring device within ameasured period of [51] f time. in a preferred embodiment, the storagemeans is con- [58] Field Of Search ..73/3, 194 R tinuany flushed withthe product flowing in the active flow path thereby maintaining thetemperature and product in the [56] defences cued storage meansconincident with the temperature and product UNITED STATES PATENTSflowing in the active flow path. additionally fluid derived from theactive flow path may be utilized for driving the in ec- 3 ....73/3 tionmeans 3,028,744 4/1962 Bagwell ....73/3 3,250,113 5/l966 Rush ..73/3

Primary ExaminerLouis R. Prince 19 Claims, 1 Drawing Figure AssistantExaminer-William A. Henry, ll Attorney-Lemer, David & Littenberg "5 54/6 f4 74 m Mi ea e/M9 JVICE 7? 7d a a z? I 2:290; Jl Ji 2 Van 5 T I I lI 50 49 I '45 I 84 1 e./ I? I 7f ig 3 J I 4? 7a 90 l \E/ l e i if '7 I24 i0 44 4 l f METER PROVING SYSTEM FIELD OF THE INVENTION Thisinvention relates to a system for proving and/or monitoring a flowmeasuring device, more commonly known as a fluid meter, and moreparticularly to such a system which can prove and/or monitor theaccuracy of such a flow measuring device while it is operated in anactive flow path.

BACKGROUND OF THE INVENTION In many flow systems it is desirable andindeed sometimes necessary to prove the accuracy of one or more of thefluid meters being utilized in the system to provide signalsrepresentative of the rate of flow of fluids therethrough. One suchsystem where the accuracy of flow meters is especially critical may befound for example in U.S. Pat. application Ser. No. 64,736 entitled LeakDetection System" filed Aug. 18, 1970 in the name of Edward L. Wrightand Eugene Meseck and assigned to the assignee of the instant invention.

The primary prior art technique for proving a fluid meter may be foundin U.S. Pat. No. 2,448,616 issued Sept. 7, 1948 to T. Oakley et al. Inthe Oakley system, a predetennined quantity of gas in injected into anempty pipe line having a meter. The meter reading is then taken todetermine if the meter is reading accurately. It will be appreciatedthat although a system like that disclosed in the Oakley patent provesor disproves the accuracy of the meter at the particular testconditions, the conclusions derived from such testing procedure have novalidity with respect to the accuracy of the flow meter over the variousranges of flow to which the meter will be exposed in actual service. Infact, it should be pointed out that manufacturers of flow metersrecognize that their meters perform differently at different ranges offlow therethrough, and accordingly most manufacturers provide theircustomers with curves indicating meter characteristics at differentrates of flow whereby the consumer can develop a K factor or errorfactor which should be utilized to correct the meter reading dependentupon the particular rate of flow the meter happens to be exposed to atthe time of measurement. This problem is further bought out in U.S. Pat.No. 2,046,591 which specifically discloses that a meter which iscalibrated in one portion of its curve will not necessarily readaccurately in other protions of its curve.

Other patents such as U.S. Pat. No. 2,510,327 entitled Testing Apparatusfor Fluid Meters and U.S. Pat. No. 3,308,660 entitled High PercisionFlow Meter disclose other techniques for proving meters and arerepresentative of other prior art techniques over which the instantinvention is intended to be an improvement. In U.S. Pat. No. 2,510,327,again the meter is tested by either removing the fluid which wasnormally flowing therein or by testing dry, both techniques beingequivalent for all practical purposes to the technique presented in theaforementioned Oakley patent. In U.S. Pat. No. 3,308,660, a meter istested by introducing a disimilar material into the active flow path forcalibration purposes. Since this system is relatively complex andexpensive to administer, it has not enjoyed acceptance in the industry.Furthermore, in the system described in U.S. Pat. No. 3,308,660 themeter thereof is not a true flow measuring device in the sense that itcannot independently produce an output signal representative of fluidflow therethrough, but can only function to monitor fluid flow when thedissimilar material is introduced therethrough.

Thus prior to the instant invention, there existed no simple,inexpensive and reliable technique for proving the accuracy of a fluidmeter disposed in and operating upon an active flow path.

SUMMARY OF THE INVENTION As suggested above, the instant inventionprovides a proving system for a flow meter which is capable of provingthe accuracy of the meter while it is situated in and operating upon anactive flow path. Thus the meter proving system of the instant inventionwill provide an indication of the accuracy of the meter at theparticular flow rate which is being detected at the time of proving. Itwill also be appreciated that by varying the flow rate in the activeflow path in which the meter is situated, it is possible, utilizing thesystem of the instant invention to actually check the validity of theaforementioned manufacturers curves. Moreover, the instant invention canbe used to continually monitor a flow meter to provide accurate flowrate information or alternatively can be employed to periodically checkthe validity of flow rate information to determine an updatedinstrumentation error factor which can be employed for example in theleak detection system of the aforementioned patent application to EdwardL. Wright et al.

Broadly speaking and in combination with a flow measuring devicesituated in an active flow path and capable of providing an indicationof the rate of flow of fluid'therethrough; the meter proving orcalibration system of the instant invention comprises storage means foraccumulating a predetermined volume of fluid and injection meanscooperating with the storage means for introducing the predeterminedvolume of fluid into the active flow path on the upstream side of theflow measuring device within a measured period of time. By sampling theflow for a period of time prior to the introduction of the predeterminedvolume of fluid and then sampling the flow measuring device during themeasured period of time that the additional predetermined volume offluid is being introduced into the flow path, it is possible todetermine the actual flow rate in the active flow path.

Preferably a bypass fluid circuit is established which includes a firstfluid path communicating at one and thereof with the active flow path onthe downstream side of the flow measuring device and at its opposite endwith the storage means, and a second fluid path communicating at one endthereof with the storage means and at the other end thereof with theactive flow path on the upstream side of the flow measuring device. Thusthe fluid bypass circuit establishes a technique for not onlyintroducing the predetermined volume of fluid into the upstream side ofthe active flow path, but additionally provides a path by which thefluid accumulated in the storage means can be tapped from the downstreamside of the active flow path. In this manner the fluid bypass circuitand the storage means disposed therein provides a simple method ofaccumulating and injecting a predetermined volume of fluid into theactive flow path and moreover guarantees that the fluid being injectedis exactly the same fluid as that flowing in the active flow path.

As a particularly advantageous feature of the instant invention aflushing" bypass flow path is provided which communicates at one endthereof with the active flow path on the downstream side of the flowmeasuring device and is selectively communicable at its other end withthe storage means. In the practice of the invention, at all times priorto and after a calibration operation; by virtue of the flushing bypassflow path, the storage means will be continually flushed with the fluidflowing in the active flow path thus guaranteeing not only theinstantaneous similarity of the injected fluid to the fluid in theactive flow path but also guaranteeing the identity of temperature ofthese two fluids.

As a further preferred embodiment of the instant invention, and as willbe explained in greater detail, the actuating means employed to injectthe predetermined volume of fluid accumulated in the storage means intothe active flow path is operated by fluid derived from the downstreamside of the active flow path. This provides an extremely simpletechnique for operating the injection means of the system.

Finally, as a further feature, means are provided to vary the measuredperiod of time during which the additional predetermined volume of fluidwill be introduced into the active flow path thereby permitting one tovary the incremental flow rate in the active flow path attributable tothe additional volume introduced therein. Preferably, the increased flowrate attributable to the injected volume is maintained as small aspossible with respect to the flow rate in the active flow path,

most desirably in a range of a l to 5 percent increase in flow rate,such that the information derived from the flow measuring device will infact be as closely related as possible to the actual flow rate in theactive flow path.

Accordingly, it is an object of the instant invention to provide a meterproving system capable of proving the meter at actual operating flowrates.

Another object of the instant invention is to provide such a meterproving system which employs storage means for accumulating apredetermined volume of fluid therein, and injection means forintroducing said predetermined volume of fluid into the active flow pathon the upstream side of the flow measuring device within a measuredperiod of time.

Another object of the instant invention is to provide such a meterproving system which includes a flushing bypass circuit to continuallyflush the aforementioned storage means with the product flowing in theactive flow path.

Another object of the instant invention is to provide such a meterproving system wherein the injection means for introducing apredetennined volume of fluid into the active flow path is operated byfluid derived from the downstream side of the flow measuring device.

Yet another object of the instant invention is to provide such a meterproving system wherein the incremental increase in flow rate in theactive flow path attributable to the predetermined volume accumulated inthe aforementioned storage means is made as small as possible preferablyin the range of l to 5 percent of the active flow rate.

These and other objects of the instant invention will be had byreferring to the following specification and drawing in which:

HO. 1 illustrates a meter proving system of the instant invention.

Turning to the Figure, there is shown a fluid flow path 12 in which issituated a flow measuring device or meter 14 capable of providing anindication of the rate of flow of fluid through the flow path 12 from aninput 16 to an output 18 thereof. The flow path 12 can be a conduit orpipe of any type and could be carrying any fluid, gas or liquid. In likemanner, the flow measuring device 14 might be any commercially availablemeter providing output signals, analog or digital, indicative of therate of flow of fluid through the flow path 12. Although in no wayintended to be limited thereby, it might be pointed out that theparticular flow measuring device 14 employed in the instant system is ameter device of the digital type providing as an output 3,000 pulses perbarrel of product flowing through the path 12. Also, since the flow path12 is carrying fluid, and indeed the meter proving system of the instantinvention is intended to be employed for testing the accuracy of thedevice 14 while the flow path 12 is carrying fluid, the path 12 willhereinafter be referred to as an active" flow path.

Disposed in parallel about the flow measuring device is a fluid bypasscircuit comprising a first fluid path broadly designated 20 and a secondfluid path broadly designated 22. As will be explained in greaterdetail, storage means 24, preferably in the form of an elongatedcylinder 26, is disposed in the fluid bypass circuit, and injectionmeans 28, preferably in the fonn of a longitudinally displaceable piston30, is provided for introducing a predetermined volume of fluid 32accumulated in the storage means 24 into the upstream side of the activeflow path 12 within a measured period of time.

The first flow path 20 is employed to divert fluid from the downstreamside of the flow measuring device 14 to the storage means 24 for theaccumulation of the predetermined volume V 32. To that end the firstfluid path 20 is connected at one end 34 thereof to the flow path 12 onthe downstream side of the flow measuring device 14, and includes, forease of identification, the following sections of conduit: the section36 including a pump 38 therein to aid in withdrawing the fluid from theline 12, and the section 40 including a normally open valve 42 therein.Thus the opposite end 44 of the first fluid path 20 is connected as aninput to the storage means 24 and may be said to be selectivelycommunicable with the storage means 24 by virtue of the valve 42. Itmight be pointed out at this time, that a normally closed valve 46dictates that the fluid in segment 36 pass to the segment 40.

As noted above, the second fluid path 22 provides the path by which theaccumulated volume V 32 in the storage means 24 may be injected into theupstream side of the flow path 12. To that end, one end 48 of the secondfluid path 22 is connected to the storage means 24, and the fluid path22 includes segments 50 and 52 whereby the opposite end 54 of the secondfluid path 22 may be selectively connectable to the flow path 12 on theupstream side of the flow measuring device 14 by virtue of operation ofa normally closed valve 56.

To complete the description of the basis apparatus necessary to practicethe instant invention, it should be pointed out that secured to thepiston 30 is a piston rod 58 carrying a switch actuating member 60 atits opposite end. As the piston 30 sweeps the entire volume of thecylinder 26, (by actuating means to be described in greater detail), thetime required to inject the smaller predetermined volume of the fluid V32 into the flow path 12 will be accurately measured by the sequentialenergization of switches 62 and 64 by the actuating member 60. Switches62 and 64 might be simple mechanical limit switches or alternativelymight comprise magnetically operable reed switches actuated in responseto the passing of the actuating member 60 constructed of suitablemagnetic material.

A pretravel distance 66 and an overtravel distance 68 are providedwithin the storage means 24 to guarantee that the piston 30 travels at aconstant rate of speed during the time that it sweeps the predetemtinedvolume V 32.

With the apparatus thus far described, the accuracy of the meter 14 canbe proven. Specifically, to determine actual flow rate through the flowmeasuring device 14, it is only necessary to take the follow steps andperform the following calculations. First the meter 14 is sampled over apredetermined time interval, for example 10 seconds, to determine theactive flow (nominal) in pulses per unit time. This may be designatedP/unit t. Then the normally closed valve 56 is opened and by actuatingmeans to be described in greater detail, the piston 30 is caused tosweep the volume of fluid which has been accumulated in the cylinder 26.As the actuating member 60 sequentially passes the switches 62 and 64,the time between the energization of these two switches will provide anexactly measured interval of time (T) during which the predeterminedvolume (V) 32 is injected into the upstream side of the active flowpath. During this time interval (T), the flow measuring device 14 isagain sampled to provide an indication of the number of pulses producedduring the interval (T) while both main stream flow and the additionalflow due to the volume V 32 are passing through the flow measuringdevice 14. This may be designated P orX. Finally, knowing now theinterval of time T, the previous sampling of the meter (taken before theinjection'of the additional volume) which produced pulses per unit timecan be converted to pulses per interval of time (T) simply bymultiplying;

P/ unit 1 x (T) to produce X which represents mainstream flow in pulsesper predetermined interval of time T. If one substracts X from X he thenknows the number of pulses produced by the meter 14, which were wereattributable to the predetermined volume V 32. This information providesa factor:

which says that the meter is passing a certain volume per pulse whichfactor can then be multiplied by X (total pulses over the interval T toprovide an indication of the actual flow rate in the meter, the desiredresult. If desired, the quantity X, representing pulses fl may bederived by taking two samplings of the meter 14, one before theinjection and one after the injection, and the results averaged.

To guarantee the instantaneous coincidence of the fluid in the storagemeans 24 to the fluid in the active flow path 12 and the coincidence ofthe temperature of these two fluids, a flushing bypass flow path 70 isprovided and communicates at one end 72 thereof with the storage means24 (through the segment 50 of the second fluid path 22) and at the otherend 74 thereof with the downstream side of the active flow path 12. Anormally open valve 76 is provided in the flushing bypass flow path 70.In operation, whenever the system is stable (i.e., the volume 32 is notbeing injected into the upstream side of the flow path 12), the normallyclosed valve 56 remains closed while the normally open valve 76 remainsopen. In this manner, fluid is continually being drawn from thedownstream side of the flow measuring device 14 (through the first fluidpath flushed through the storage means 24, through the flushing bypassflow path 70, and back to the downstream side of the active flow path12. Thus at the instant the calibration cycle is to begin (and the valve56 is to be opened and the valve 76 closed), the sample of fluid in thestorage means will be the most recent specimen, in both properties andtemperature, of the fluid flowing in the active flow path 12.

As noted previously, the system of the instant invention furthercontemplates that the fluid flowing in the active flow path may beutilized as the actuating driving means for the injection means 28. Tothis end, there is provided an actuating bypass fluid circuit 78communicating at one end 80 thereof with the cylinder 26 on the righthand side of the piston 30 and at the other end 82 thereof with thedownstream side of the active flow path (through the segment 36 of theaforementioned first fluid path 20). When it is desired to drive theinjection means 28, the normally open valve 42 is closed, the normallyclosed valve 46 is opened, and a normally open valve 84 is closed todivert the fluid from the downstream side of the active flow path 12through the actuating bypass fluid circuit 78 to displace and drive thepiston 30. Of course, while the piston is being driven, theaforementioned normally open flushing valve 76 is closed and thenormally closed valve 56 is opened to allow the fluid stored in thestorage means 24 to be injected into the active flow path 12 aspreviously described.

After the calibration cycle is completed, a third switch 86 is trippedby the actuating member 60 to close valve 46 and open valve 42 to permitfluid to re-enter the storage means 24 from the point 44 and drive thepiston 30 rearwardly toward the position illustrated in the Figure.Simultaneously, the normally open valve 84 is permitted to revert to itsnormally open condition to provide a bleed off path through segments 78and 36 back to the downstream side of the active flow path 12. Also, itwill be appreciated that a normally open valve 88 is maintained closedat this time to prevent the fluid being used to drive the piston 30 backto its starting position from entering the second fluid path 22.

Finally, from the above discussion, it will be appreciated that the timeinterval which is required to inject the volume V 32 into the upstreamside of the active flow path 12 will determine the incremental flow rate(V which is being added to the flow rate normally carried in the activeflow path 12. Since it is a feature of the instant invention that thesystem hereof can accurately determine or test for flow rates at theactual operating point of the flow measuring device being tested, it isextremely desirable that the additional flow rate added to the activeline be maintained as small as possible. To that end, a selectivelyadjustable valve 90 is located on the output side of the pump 38 toallow one to selectively vary the actuating pressure being applied tothe rear of the piston 30 through the actuating bypass fluid path 78.Should the flow path 12 be carrying fluid at a relatively high flowrate, then the added flow rate attributable to the fluid in the volume24 will have relatively little effect on changing the actual flow ratein the active flow path 12. In that case, the selectively operable valve90 may be employed in such a manner as to increase the speed of travelof the piston 30. On the other hand, with low flow rates in the activeflow path 12, a significantly large additional flow rate due to thevolume in the storage means 24 might significantly change the operatingpoint of the flow measuring device. In that situation, the valve 90would be restricted to produce a relatively slow displacement of thepiston 30. Preferably, the valve 90 is employed in the aforedescribedmanner such that the incremental flow rate added to the line 12 byvirtue of the volume in the storage means 24 will be as small aspossible preferably in the range of l to 5 percent of the actual flowrate in the flow path 12. In this manner, the meter 14 will indeed betested at as close as possible to its actual operating point. Also, itshould be pointed out that if desired, the adjustable valve could be aservo-type mechanism automatically functioning in response to increasesand decrease in flow rate of the active line 12.

Although this invention has been described with respect to its preferredembodiments, it should be understood that many variations andmodifications will now be obvious to those skilled in the art, and it ispreferred, therefore, that the scope of the invention be limited, not bythe specific disclosure herein, only by the appended claims.

We claim:

1. In combination with a flow measuring device situated in an activeflow path and capable of providing an indication of the rate of flow offluid therethrough; a calibration system for proving said flow measuringdevice, said system comprising:

storage means for accumulating a predetermined volume of fluid therein;

injection means cooperating with said storage means for introducing saidpredetermined volume of fluid into said active flow path on the upstreamside of said flow measuiring device within a measured period of time;

wherein the fluid stored in said storage means is the same fluid flowingin said fluid path.

2. In the combination of claim 1 and further including a fluid bypasscircuit including;

a first fluid path communicating at one end thereof with said activeflow path on the downstream side of said flow measuring device andselectively connectable at its opposite end thereof to said storagemeans; and

a second fluid path communicating at one end thereof with said storagemeans and selectively connectable at its opposite end thereof to saidactive flow path on the upstream side of said flow measuring device.

3. In the combination of claim 2 and further including pumping means foraiding in the flow of fluid from said active flow path through saidfluid bypass circuit and said storage means disposed therein.

4. In the combination of claim 2 and further including a flushing bypassflow path communicating at one end with said active flow path on thedownstream side of said flow measuring device and selectivelycommunicable at its other end with said storage means;

whereby said storage means can be continually flushed with said fluidprior to the time that the fluid in said storage means is introducedinto said active flow path by said second fluid path.

5. In the combination of claim 4 wherein said other end of said flushingbypass flow path is selectively communicable with said storage means bybeing selectively connectable to said second fluid path at a pointintermediate said storage means and said active flow path.

6. In the combination of claim 5 wherein said injection means comprisesfluid displacing means operable within said storage means for displacingfluid out of said storage means; and

further including selectively operable actuating means for operatingsaid fluid displacing means.

7. In the combination of claim 6 and further including an ac tuatingbypass fluid circuit communicating at one end thereof with said storagemeans in operative relationship to said fluid displacing means andselectively communicable at its other end thereof to said downstreamside of said active flow path.

8. In the combination of claim 7 wherein said other end of saidactuating bypass fluid circuit is selectively communicable with saiddownstream side of said active flow path by being selectivelyconnectable to said first fluid path at a point intermediate saidstorage means and said active flow path.

9. In the combination of claim 8 and further including pumping meansdisposed in said first fluid path.

10. In the combination of claim 7 wherein said storage means comprisesan elongated cylinder having an internal volume greater than saidpredetermined volume;

said fluid displacing means comprises a piston longitudinally movable insaid cylinder in response to the flow of fluid into said storage meansfrom said actuating bypass fluid circuit; and

further including control means responsive to the movement of saidpiston for establishing said measured period of time within which saidpredetermined volume of fluid will be introduced into the upstream sideof said active flow path.

11. In the combination of claim 7 wherein said actuating bypass fluidcircuit includes control valve means therein for preselectively varyingthe time required for said fluid displacing means to displace saidpredetermined volume; whereby said measured period of time can bepreselectively varied to vary the increased flow rate in said activeflow path attributable to said predetermined volume of fluid.

12. In the combination of claim 11 wherein said control valve means isemployed to increase the flow rate in said active flow path attributableto said predetermined value by a magnitude between 1 and 5 percent ofthe active flow rate.

13. in the combination of claim 6 and further including meanscooperating with said actuating means for preselectively varying saidmeasured period of time; whereby the increased flow rate in said activeflow path attributable to said predetermined volume of fluid can bevaried.

14. In the combination of claim 13 wherein said last named means isemployed to increase the flow rate in said active flow path attributableto said predetermined valve by a magnitude between I and 5 percent ofthe active flow rate.

15. In the combination of claim 2 wherein said injection means comprisesfluid displacing means operable within said storage means for displacingfluid out of said storage means; and

further including selectively operable actuating means for operatingsaid fluid displacing means.

16. In the combination of claim 15 and further including an actuatingbypass fluid circuit communicating at one end thereof with said storagemeans in operative relationship to said fluid displacing means andselectively communicable at its other end thereof to said downstreamside of said active flow path.

17. In the combination of claim 16 wherein said other end of saidactuating bypass fluid circuit is selectively communicable with saiddownstream side of said active flow path by being selectivelyconnectable to said first fluid path at a point intermediate saidstorage means and said active flow path.

18. A method of proving a flow measuring device situated in an activeflow path and capable of providing an output signal indicative of therate of flow of fluid therethrough; said method comprising the steps of:

detecting the output signal of said flow measuring device over a knownperiod of time while said fluid in said active flow path is flowingthrough said flow measuring device to provide a first valuerepresentative of output signals per unit of time for mainstream flow;

adding a predetermined volume of fluid to said flow path on the upstreamside of said flow measuring device during a measured time interval;

detecting the output signal of said flow measuring device over saidmeasured period of time to provide a second value representative ofoutput signals per measured period of time for mainstream flow plusadditional flow;

and further including the step of: converting said first valuerepresentative of output signals per measured period of time formainstream flow.

19. The method of claim 18 and further including the steps subtractingsaid third value from said second value to determine a factorrepresentative of the number of output signals produced by saidflow-measuring device attributable to said predetermined volume andmultiplying said factor by said third value to determine the active flowrate per unit time through said flow measuring device.

* a: 0: =a a

1. In combination with a flow measuring device situated in an activeflow path and capable of providing an indication of the rate of flow offluid therethrough; a calibration system for proving said flow measuringdevice, said system comprising: storage means for accumulating apredetermined volume of fluid therein; injection means cooperating withsaid storage means for introducing said predetermined volume of fluidinto said active flow path on the upstream side of said flow measuiringdevice within a measured period of time; wherein the fluid stored insaid storage means is the same fluid flowing in said fluid path.
 2. Inthe combination of claim 1 and further including a fluid bypass circuitincluding; a first fluid path communicating at one end thereof with saidactive flow path on the downstream side of said flow measuring deviceand selectively connectable at its opposite end thereof to said storagemeans; and a second fluid path communicating at one end thereof withsaid storage means and selectively connectable at its opposite endthereof to said active flow path on the upstream side of said flowmeasuring device.
 3. In the combination of claim 2 and further includingpumping means for aiding in the flow of fluid from said active flow paththrough said fluid bypass circuit and said storage means disposedtherein.
 4. In the combination of claim 2 and further including aflushing bypass flow path communicating at one end with said active flowpath on the downstream side of said flow measuring device andselectively communicable at its other end with said storage means;whereby said storage means can be continually flushed with said fluidprior to the time that the fluid in said storage means is introducedinto said active flow path by said second fluid path.
 5. In thecombination of claim 4 wherein said other end of said flushing bypassflow path is selectively communicable with said storage means by beingselectively connectable to said second fluid path at a pointintermediate said storage means and said active flow path.
 6. In thecombination of claim 5 wherein said injection means comprises fluiddisplacing means operable within said storage means for displacing fluidout of said storage means; and further including selectively operableactuating means for operating said fluid displacing means.
 7. In thecombination of claim 6 and further including an actuating bypass fluidcircuit communicating at one end thereof with said storage means inoperative relationship to said fluid displacing means and selectivelycommunicable at its other end thereof to said downstream side of saidactive flow path.
 8. In the combination of claim 7 wherein said otherend of said actuating bypass fluid circuit is selectively communicablewith said downstream side of said active flow path by being selectivelyconnectable to said first fluid path at a point intermediate saidstorage means and said active flow path.
 9. In the combination of claim8 and further including pumping means disposed in said first fluid path.10. In the combination of claim 7 wherein said storage means comprisesan elongated cylinder having an internal volume greater than saidpredetermined volume; said fluid displacing means comprises a pistonlongitudinally movable in said cylinder in response to the flow of fluidinto said storage means from said actuating bypass fluid circuit; andfurther including control means responsive to the movement of saidpiston for establishing said measured period of time within which saidpredetermined volume of fluid will be introduced into the upstream sideof said active flow path.
 11. In the combination of claim 7 wherein saidactuating bypass fluid circuit includes control valve means therein forpreselectively varying the time required for said fluid displacing meansto displace said predetermined volume; whereby said measured period oftime can be preselectively varied to vary the increased flow rate insaid active flow path attributable to said predetermined volume offluid.
 12. In the combination of claim 11 wherein said control valvemeans is employed To increase the flow rate in said active flow pathattributable to said predetermined value by a magnitude between 1 and 5percent of the active flow rate.
 13. In the combination of claim 6 andfurther including means cooperating with said actuating means forpreselectively varying said measured period of time; whereby theincreased flow rate in said active flow path attributable to saidpredetermined volume of fluid can be varied.
 14. In the combination ofclaim 13 wherein said last named means is employed to increase the flowrate in said active flow path attributable to said predetermined valveby a magnitude between 1 and 5 percent of the active flow rate.
 15. Inthe combination of claim 2 wherein said injection means comprises fluiddisplacing means operable within said storage means for displacing fluidout of said storage means; and further including selectively operableactuating means for operating said fluid displacing means.
 16. In thecombination of claim 15 and further including an actuating bypass fluidcircuit communicating at one end thereof with said storage means inoperative relationship to said fluid displacing means and selectivelycommunicable at its other end thereof to said downstream side of saidactive flow path.
 17. In the combination of claim 16 wherein said otherend of said actuating bypass fluid circuit is selectively communicablewith said downstream side of said active flow path by being selectivelyconnectable to said first fluid path at a point intermediate saidstorage means and said active flow path.
 18. A method of proving a flowmeasuring device situated in an active flow path and capable ofproviding an output signal indicative of the rate of flow of fluidtherethrough; said method comprising the steps of: detecting the outputsignal of said flow measuring device over a known period of time whilesaid fluid in said active flow path is flowing through said flowmeasuring device to provide a first value representative of outputsignals per unit of time for mainstream flow; adding a predeterminedvolume of fluid to said flow path on the upstream side of said flowmeasuring device during a measured time interval; detecting the outputsignal of said flow measuring device over said measured period of timeto provide a second value representative of output signals per measuredperiod of time for mainstream flow plus additional flow; and furtherincluding the step of: converting said first value representative ofoutput signals per measured period of time for mainstream flow.
 19. Themethod of claim 18 and further including the steps of: subtracting saidthird value from said second value to determine a factor representativeof the number of output signals produced by said flow measuring deviceattributable to said predetermined volume; and multiplying said factorby said third value to determine the active flow rate per unit timethrough said flow measuring device.